Roles of PLC-γ2 and PKCα in TPA-induced apoptosis of gastric cancer cells

Rediscovery of Traditional Plant Medicine: An Underestimated Anticancer Drug of Chelerythrine

In many studies, the extensive and significant anticancer activity of chelerythrine (CHE) was identified, which is the primary natural active compound in four traditional botanical drugs and can be applied as a promising treatment in various solid tumors. So this review aimed to summarize the anticancer capacities and the antitumor mechanism of CHE. The literature searches revolving around CHE have been carried out on PubMed, Web of Science, ScienceDirect, and MEDLINE databases. Increasing evidence indicates that CHE, as a benzophenanthridine alkaloid, exhibits its excellent anticancer activity as CHE can intervene in tumor progression and inhibit tumor growth in multiple ways, such as induction of cancer cell apoptosis, cell cycle arrest, prevention of tumor invasion and metastasis, autophagy-mediated cell death, bind selectively to telomeric G-quadruplex and strongly inhibit the telomerase activity through G-quadruplex stabilization, reactive oxygen species (ROS), mitogen-activated protein kinase (MAPK), and PKC. The role of CHE against diverse types of cancers has been investigated in many studies and has been identified as the main antitumor drug candidate in drug discovery programs. The current complex data suggest the potential value in clinical application and the future direction of CHE as a therapeutic drug in cancer. Furthermore, the limitations and the present problems are also highlighted in this review. Despite the unclearly delineated molecular targets of CHE, extensive research in this area provided continuously fresh data exploitable in the clinic while addressing the present requirement for further studies such as toxicological studies, combination medication, and the development of novel chemical methods or biomaterials to extend the effects of CHE or the development of its derivatives and analogs, contributing to the effective transformation of this underestimated anticancer drug into clinical practice. We believe that this review can provide support for the clinical application of a new anticancer drug in the future.

Connection of BANK1, Tolerance, Regulatory B cells, and Apoptosis: Perspectives of a Reductionist Investigation

BANK1 transcript is upregulated in whole blood after kidney transplantation in tolerant patients. In comparison to patients with rejection, tolerant patients display higher level of regulatory B cells (Bregs) expressing granzyme B (GZMB⁺) that have the capability to prevent effector T cells proliferation. However, BANK1 was found to be decreased in these GZMB⁺ Bregs. In this article, we investigated seven different transcriptomic studies and mined the literature in order to make link between BANK1, tolerance and Bregs. As for GZMB⁺ Bregs, we found that BANK1 was decreased in other subtypes of Bregs, including IL10⁺ and CD24^hiCD38^hi transitional regulatory B cells, along with BANK1 was down-regulated in activated/differentiated B cells, as in CD40-activated B cells, in leukemia and plasma cells. Following a reductionist approach, biological concepts were extracted from BANK1 literature and allowed us to infer association between BANK1 and immune signaling pathways, as STAT1, FcγRIIB, TNFAIP3, TRAF6, and TLR7. Based on B cell signaling literature and expression data, we proposed a role of BANK1 in B cells of tolerant patients that involved BCR, IP3R, and PLCG2, and a link with the apoptosis pathways. We confronted these data with our experiments on apoptosis in total B cells and Bregs, and this suggests different involvement for BANK1 in these two cells. Finally, we put in perspective our own data with other published data to hypothesize two different roles for BANK1 in B cells and in Bregs.

Insight into the genetic etiology of Alzheimer's disease: A comprehensive review of the role of rare variants

Early-onset Alzheimer's disease (EOAD) is generally known as a dominant disease due to highly penetrant pathogenic mutations in the amyloid precursor protein, presenilin 1 and 2. However, they explain only a fraction of EOAD patients (5% to 10%). Furthermore, only 10% to 15% of EOAD families present with clear autosomal dominant inheritance. Studies showed that only 35% to 60% of EOAD patients have at least one affected first-degree relative. Parent-offspring concordance in EOAD was estimated to be <10%, indicating that full penetrant dominant alleles are not the sole players in EOAD. We aim to summarize current knowledge of rare variants underlying familial and seemingly sporadic Alzheimer's disease (AD) patients. Genetic findings indicate that in addition to the amyloid beta pathway, other pathways are of importance in AD pathophysiology. We discuss the difficulties in interpreting the influence of rare variants on disease onset and we underline the value of carefully selected ethnicity-matched cohorts in AD genetic research.

Preeclampsia serum induces human glomerular vascular endothelial cell hyperpermeability via the HMGB1-Caveolin-1 pathway

To explore new ideas about the pathogeny of preeclampsia (PE) proteinuria, this study focused on whether severe PE serum (PES) could induce high-molecular-weight protein (HMWP) hyperpermeability in glomerular endothelial cells (GEC) via the HMGB1-Caveolin-1 (CAV-1) pathway. Normal pregnancy serum (NPS) and severe PES were used to treat primary human GEC monolayer for 24 h. The CAV-1 inhibitor methyl-beta-cyclodextrin (MBCD), the HMGB1 inhibitor glycyrrhizicacid (GA), recombinant HMGB1 (rHMGB1) were also used to treat GEC monolayer that were stimulated by NPS or severe PES. The dynamic permeability of GEC to HMWP was detected by Evans blue-labeled BSA and CAV-1 expression in GEC was analyzed by immunofluorescence staining and Western blotting. We detected HMGB1 expression in placenta and serum in normal pregnancy and severe PE. The results showed that severe PES significantly promoted GEC hyperpermeability and CAV-1 expression. By inhibiting CAV-1 expression, MBCD reversed severe PES-induced GEC monolayer permeability. HMGB1 expression in PE placenta and serum was significantly increased. Compared with that in normal placenta, HMGB1expression was increased in the cytoplasm of syncytiotrophoblast cells in PE placenta. GA decreased the severe PES-induced hyperpermeability and CAV-1 expression in GEC. rHMGB1 induced high expression levels of CAV-1 and HMWP hyperpermeability in GEC. In conclusion, HMGB1 is increased in severe PE patients and induces the expression of CAV-1 in GEC. High expression of CAV-1 in GEC can promote HMWP hyperpermeability, which may contribute to the development of PE proteinuria.

PLCγ2 promotes apoptosis while inhibits proliferation in rat hepatocytes through PKCD/JNK MAPK and PKCD/p38 MAPK signalling

OBJECTIVES

The PLCG2 (PLCγ2) gene is a member of PLC gene family encoding transmembrane signalling enzymes involved in various biological processes including cell proliferation and apoptosis. Our earlier study indicated that PLCγ2 may be involved in the termination of regeneration of the liver which is mainly composed of hepatocytes, but its exact biological function and molecular mechanism in liver regeneration termination remains unclear. This study aims to examine the role of PLCγ2 in the growth of hepatocytes.

MATERIALS AND METHODS

A recombinant adenovirus expressing PLCγ2 was used to infect primary rat hepatocytes. PLCγ2 mRNA and protein levels were detected by qRT-PCR and Western blot. The subcellular location of PLCγ2 protein was tested by an immunofluorescence assay. The proliferation of hepatocytes was measured by MTT assay. The cell cycle and apoptosis were analysed by flow cytometry. Caspase-3, -8 and -9 activities were measured by a spectrophotometry method. Phosphorylation levels of PKCD, JNK and p38 in the infected cells were detected by Western blot. The possible mechanism underlying the role of PLCγ2 in hepatocyte growth was also explored by adding a signalling pathway inhibitor.

RESULTS

Hepatocyte proliferation was dramatically reduced, while cell apoptosis was remarkably increased. The results demonstrated that PLCγ2 increased the phosphorylation of PKCD, p38 and JNK in rat hepatocytes. After PKCD activity was inhibited by the inhibitor Go 6983, the levels of both p-p38 and p-JNK MAPKs significantly decreased, and PLCγ2-induced cell proliferation inhibition and cell apoptosis were obviously reversed.

CONCLUSIONS

This study showed that PLCγ2 regulates hepatocyte growth through PKCD-dependently activating p38 MAPK and JNK MAPK pathways; this result was experimentally based on the further exploration of the effect of PLCγ2 on hepatocyte growth in vivo.

Silencing of phospholipase C gamma 2 promotes proliferation of rat hepatocytes in vitro

The management of hepatic failure is undoubtedly difficult, and poor results have led to the search for novel therapeutic approaches. Nowadays, anti-apoptotic gene therapy is considered as an ideal approach. It has been proved that phospholipase Cγ2 (PLCγ2) is involved in the apoptosis of immune cells and tumor cells; however, whether this gene is related to hepatocyte death is still unclear. This study examined the role of PLCγ2 by inhibiting its expression in rat hepatocytes with siRNA. We also further analyzed the cellular mechanism by which the expression inhibition of PLCγ2 induces cell death. Silencing PLCγ2 gene by adenovirus vector expressing PLCγ2-targeted siRNA caused the great decline in the number of G1- and G2/M phase cells, the significant increase in the number of S phase cells, and the obvious reduction in apoptosis index. In addition, silencing PLCγ2 gene relieved the rat hepatocyte damage, such as the cell shrinkage and chromatin condensation, nuclear fragmentation. Further analysis of Ad-PLCγ2 siRNA-transfected hepatocytes demonstrated that suppression of PLCγ2 gene expression could cause the caspase dependent cell death by inhibiting the signal pathway MEKK1/MKK4/JNK1/2/c-Jun. In conclusion, these findings suggest that interference with PLCγ2 expression could relieve the inhibitory effect of PLCγ2 on hepaocyte apoptosis, thus, promote proliferation through inactivating PKCδ-mediated JNK1/2 signaling pathway.

Enhancement or inhibition of PLCγ2 expression in rat hepatocytes by recombinant adenoviral vectors that contain full-length gene or siRNA

We investigated the effects of recombinant adenovirus vectors that overexpress or silence PLCγ2 on the expression of this gene during hepatocyte proliferation. Hepatocytes were isolated, identified by immunofluorescent cytochemical staining and infected by previously constructed Ad-PLCγ2 and Ad-PLCγ2 siRNA1, siRNA2 and siRNA3. Green fluorescent protein (GFP) expression was observed by fluorescence microscopy. Infection percentage was calculated by flow cytometry. mRNA and protein levels of PLCγ2 were detected by quantitative reverse transcription-PCR (qRT-PCR) and western blotting, respectively. The viability of the infected hepatocytes was measured by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. We found that nearly 97% of cells were positive for the hepatocyte marker, CK18. After infection of Ad-PLCγ2 and Ad-PLCγ2 siRNA, more than 99% of hepatocytes expressed GFP significantly, and mRNA and protein expression of PLCγ2 was up-regulated significantly in Ad-PLCγ2 infected hepatocytes, but down-regulated in Ad-PLCγ2 siRNA2 infected cells. The cell proliferation rate decreased in PLCγ2-overexpressing cells, while the rate increased in PLCγ2-silencing cells. We verified that recombinant Ad-PLCγ2 and Ad-PLCγ2 siRNA2 were constructed successfully. These two recombinant vectors promoted or decreased the expression of PLCγ2 in rat hepatocytes and affected the cell proliferation rate, which provides a useful tool for further investigation of the role of PLCγ2 in hepatocyte apoptosis.

TFF3-dependent resistance of human colorectal adenocarcinoma cells HT-29/B6 to apoptosis is mediated by miR-491-5p regulation of lncRNA PRINS

Tumour necrosis factor-α (TNF-α) is a double-edged cytokine associated with pathogenesis of inflammatory-related cancers being also able to induce cancer cell death. In the process of tumour development or metastasis, cancer cells can become resistant to TNF-α. In trefoil factor 3 (TFF3) overexpressing colorectal adenocarcinoma cells (HT-29/B6), we observed enhanced resistance against TNF-α/interferon gamma-induced apoptosis. TFF3 is a secreted small peptide that supports intestinal tissue repair but is also involved in intestinal tumour progression and scattering. We hypothesised that TFF3 rescues intestinal epithelial cancer cells from TNF-α-induced apoptosis by involving regulatory RNA networks. In silico-based expression analysis revealed TFF3-mediated regulation of selected microRNAs as well as long non-coding RNAs (lncRNAs), whereas miR-491-5p was identified to target the lncRNA ‘psoriasis susceptibility-related RNA gene induced by stress’ (PRINS). RNA interference-based gain- and loss-of-function experiments examined miR-491-PRINS axis to exert the TFF3-mediated phenotype. Chemical inhibition of selected pathways showed that phosphatidylinositol 3-kinase/AKT accounts for TFF3-mediated downregulation of miR-491-5p and accumulation of PRINS. Moreover, we showed that PRINS colocalises with PMAIP1 (NOXA) in nuclei of HT-29/B6 possessing inhibitory effects. Immunoprecipitation experiments proved molecular interaction of PMAIP1 with PRINS. Our study provides an insight into RNA regulatory networks that determine resistance of colorectal cancer cells to apoptosis.

Lentivirus-mediated PLCγ1 gene short-hairpin RNA suppresses tumor growth and metastasis of human gastric adenocarcinoma

Targeted molecular therapy has gradually been a potential solution in cancer therapy. Other authors' and our previous studies have demonstrated that phosphoinositide-specific phospholipase γ (PLCγ) is involved in regulating tumor growth and metastasis. However, the molecular mechanism underlying PLCγ-dependent tumor growth and metastasis of gastric adenocarcinoma and whether PLCγ may be a potential target for tumor therapy in human gastric adenocarcinoma are not yet well determined. Here, we investigated the role of PLCγ inhibition in tumor growth and metastasis of human gastric adenocarcinoma using BGC-823 cell line and a nude mouse tumor xenograft model. The results manifested that the depletion of PLCγ1 by the transduction with lentivirus-mediated PLCγ1 gene short-hairpin RNA (shRNA) vector led to the decrease of tumor growth and metastasis of human gastric adenocarcinoma in vitro and in vivo. Furthermore, the Akt/Bad, Akt/S6, and ERK/Bad signal axes were involved in PLCγ1-mediated tumor growth and metastasis of human gastric adenocarcinoma. Therefore, the abrogation of PLCγ1 signaling by shRNA could efficaciously suppress human gastric adenocarcinoma tumor growth and metastasis, with important implication for validating PLCγ1 as a potential target for human gastric adenocarcinoma.

Gene expression profiling analysis of osteosarcoma cell lines

Osteosarcoma (OS) is the most common type of primary bone malignancy and has a poor prognosis. To investigate the mechanisms of osteosarcoma, the present analyzed the GSE28424 microarray. GSE28424 was downloaded from the Gene Expression Omnibus, and included a collective of 19 OS cell lines and four normal bone cell lines, which were used as controls. Subsequently, the differentially expressed genes (DEGs) were screened using the Limma package in Bioconductor. Gene Ontology (GO) and pathway enrichment analysis of the DEGs was performed using the Database for Annotation, Visualization and Integrated Discovery, interactions between the proteins encoded by the DEGs were identified using STRING, and the protein‑protein interaction (PPI) network was visualized using Cytoscape. In addition, modular analysis of the PPI network was performed using the Clique Percolation Method (CPM) in CFinder. A total of 1,170 DEGs were screened, including 530 upreguated and 640 downregulated genes. The enriched functions included organelle fission, immune response and response to wounding. In addition, RPL8 was observed to be involved with the ribosomal pathway in module A of the PPI network of the DEGs. PLCG1, SYK and PLCG2 were also involved in the B‑cell receptor signaling pathway in module B and the Fc‑epsilon RI signaling pathway in module C. In addition, AURKA (degree=39), MAD2L1 (degree=38), CDCA8 (degree=38), BUB1 (degree=37) and MELK (degree=37) exhibited higher degrees of connectivity in module F. The results of the present study suggested that the RPL8, PLCG1, PLCG2, SYK, MAD2L1, AURKA, CDCA8, BUB1 and MELK genes may be involved in OS.

Clinicopathological correlation and prognostic significance of protein kinase cα overexpression in human gastric carcinoma

OBJECTIVES

This study investigated the PKCα protein expression in gastric carcinoma, and correlated it with clinicopathological parameters. The prognostic significance of PKCα protein expression in gastric carcinoma was analyzed.

METHODS

Quantitative real-time PCR test was applied to compare the PKCα mRNA expression in tumorous and nontumorous tissues of gastric carcinoma in ten randomly selected cases. Then PKCα protein expression was evaluated in 215 cases of gastric carcinoma using immunohistochemical method. The immunoreactivity was scored semiquantitatively as: 0 = absent; 1 = weak; 2 = moderate; and 3 = strong. All cases were further classified into two groups, namely PKCα overexpression group with score 2 or 3, and non-overexpression group with score 0 or 1. The PKCα protein expression was correlated with clinicopathological parameters. Survival analysis was performed to determine the prognostic significance of PKCα protein expression in patients with gastric carcinoma.

RESULTS

PKCα mRNA expression was upregulated in all ten cases of gastric carcinoma via quantitative real-time PCR test. In immunohistochemical study, eighty-eight out of 215 cases (41%) of gastric carcinoma revealed PKCα protein overexpression, which was statistically correlated with age (P = 0.0073), histologic type (P<0.0001), tumor differentiation (P = 0.0110), depth of invasion (P = 0.0003), angiolymphatic invasion (P = 0.0373), pathologic stage (P = 0.0047), and distant metastasis (P = 0.0048). We found no significant difference in overall and disease free survival rates between PKCα overexpression and non-overexpression groups (P = 0.0680 and 0.0587). However, PKCα protein overexpression emerged as a significant independent prognostic factor in multivariate Cox regression analysis (hazard ratio 0.632, P = 0.0415).

CONCLUSIONS

PKCα protein is upregulated in gastric carcinoma. PKCα protein expression is statistically correlated with age, histologic type, tumor differentiation, depth of invasion, angiolymphatic invasion, pathologic stage, and distant metastasis. The PKCα protein overexpression in patients with gastric carcinoma is a significant independent prognostic factor in multivariate Cox regression analysis.

Bcl-2 mediated modulation of vascularization in prostate cancer xenografts

PURPOSE

We previously demonstrated that Bcl-2 overexpression enhances the radiation resistance of PC-3 human prostate cancer cells and xenografts by inhibiting apoptosis, increasing proliferation, and promoting angiogenesis. To further elucidate the relationship between Bcl-2 expression and the angiogenic potential of PC-3-Bcl-2 cells, tumorigenicity, angiogenesis, and lymphangiogenesis were evaluated and compared in a Bcl-2 overexpressing clone in vitro and in vivo.

EXPERIMENTAL DESIGN

Human prostate cancer cells over expressing Bcl-2 were studied in vitro and in vivo to determine the angiogenic and lymphangiogenic properties of these cells.

RESULTS

Increased Bcl-2 expression enhanced the tumorigenicity of prostate cancer xenografts. It also enhanced the expression and secretion of key angiogenic and lymphangiogenic factors that stimulated the synthesis of CD31-positive blood vessels and LYVE-1 positive lymphatics. Specifically, the increased angiogenic and lymphangiogenic potential correlated with increased serum levels of basic fibroblast growth factor (bFGF), interleukin 8 (CXCL8), and matrix metalloproteinase (MMP 9). In vitro analysis demonstrated that Bcl-2 expressing tumor cells secreted bFGF and vascular endothelial growth factor (VEGF) into culture supernatants. Microarray analysis of Bcl-2 expressing PC-3 cells demonstrated increased transcription of genes involved in metabolism, such as interleukins, growth factors, tumor necrosis factors (TNF) family members, and peptidases.

CONCLUSIONS

Together, these results demonstrate that Bcl-2 can regulate tumoral angiogenesis and lymphangiogenesis and suggest that therapy targeted at Bcl-2 expression, angiogenesis, and lymphangiogenesis may synergistically modulate tumor growth and confirm that Bcl-2 is a pivotal target for cancer therapy.

In vivo transfection of C/EBP-alpha gene could ameliorate CCL(4)-induced hepatic fibrosis in mice

AIM

Hepatic stellate cells (HSCs) play a key role in liver fibrosis. CCAAT/enhancer-binding proteins-alpha (C/EBP-alpha) can inhibit HSCs activation in vitro, as described in our previous study. However, little is known about the in vivo effect of C/EBP-alpha gene in hepatic fibrosis.

METHODS

Male BALB/c mice were injected by hydrodynamic protocol with pIRES2-EGFP-C/EBPalpha expression vector from the first to the fourth week (early intervention) or from the ninth to the 12th week (late intervention) after CCl(4) injection, respectively. Successful transfection of vector and the expression of C/EBP-alpha were confirmed with the appearance of green fluorescence in liver cells, immunohistochemical staining and the western blot.

RESULTS

High expression of C/EBP-alpha gene in liver cells, especially in non-parenchymal cells, could reduce the content of collagens by 82.5% and 72.3% (Sirius red staining + image analysis) and the content of hydroxyproline by 56.3% and 51.6%, respectively, in the early and late intervention experiments.

CONCLUSION

It is evident that exogenous C/EBP-alpha gene has an early and late intervention role in mice liver fibrosis.

Identification and analysis of the promoter region of the human PLC-δ4 gene

The delta4 isoform of phospholipase C (PLC-delta4) is thought to be associated with various cellular functions and disease status. However, little is known about how its function is controlled in cells, particularly in terms of the regulation of its expression. To understand the regulation mechanisms of the PLC-delta4 gene transcription, the 5'-flanking region (-2046 approximately +5) (the nucleotide sequence data reported in this paper have been submitted to the EMBL/GenBank/DDBJ data bank under accession numbers DQ302751) of the human PLC-delta4 gene was isolated from human genomic DNA. It was a TATA-less promoter with very GC-rich sequences near the transcription start site. The activity of the PLC-delta4 promoter was shown in various human and mouse cell lines by luciferase reporter assay. Serial deletion analysis identified the core promoter region as being between -402 and -67, in which an E-box and an AP-1 binding site played important roles in the promoter activity. In addition, we also showed that 12-O-tetradecanoylphorbol-1,3-acetate (TPA), a PKC activator and tumor promoter, induced the activity of the PLC-delta4 promoter via the AP-1 binding site. In summary, this study identified a core promoter region of the hPLC-delta4 gene and the factor binding sites responsible for the promoter activity. These results will provide important new information to further understand the regulatory mechanism of the PLC-delta4 function.

Effect of protein kinase C alpha, caspase-3, and survivin on apoptosis of oral cancer cells induced by staurosporine

AIM

To elucidate inhibition of protein kinase C alpha (PKC alpha) activity by staurosporine on apoptosis of oral cancer cell line tongue squamous cell carcinoma (TSCCa) cells and to clarify the role of survivin and caspase-3 in mediating apoptosis.

METHODS

TSCCa cell viability was measured by MTT assay after 100 nmol/L staurosporine treatment. Apoptotic cells were identified by using phase contrast microscopy, acridine orange/ethidium bromide staining, and flow cytometry. Level of PKC alpha and its subcellular location were investigated using Western blot analysis. Expression of survivin and caspase-3 were evaluated using immunocytochemistry.

RESULTS

Staurosporine significantly inhibited the cell viability of TSCCa cells in a dose- and time-dependent manner. Marked cell accumulation in G2/M phase was observed after 100 nmol/L staurosporine exposure for 6 h and 12 h. In addition, the percentage of apoptosis increased in a time-dependent manner, from 2.9% in control cultures to approximately 27.4% at 100 nmol/L staurosporine treatment for 24 h. Staurosporine displayed difference in inhibitory efficacy between cytosolic and membrance-derived PKC alpha. The content of PKCalpha in membrane versus cytosol decreased quickly, from 0.45 in ethanol-treated control cultures to 0.18 after staurosporine exposure for 24 h (P<0.01). After treatment with staurosporine, a time-dependent reduction of survivin and an activation of caspase-3 were observed in TSCCa cells.

CONCLUSION

Staurosporine inhibited cell viability and promoted apoptosis in TSCCa cells. Inhibition of PKCalpha activity might be a potential mechanism for staurosporine to induce apoptosis in this cell line. The cleavage of survivin and activation of caspase-3 signaling pathway might contribute to PKC alpha inhibition-induced apoptosis.

A comparative study of the effect of the antineoplastic ether lipid 1-O-octadecyl-2-O-methyl-glycero-3-phosphocholine and some homologous compounds on PKCα and PKCɛ

The effects of the anti-neoplastic ether lipid ET-18-OCH3 and some structural homologues on the activity of protein kinase C alpha (PKC alpha) were studied and compared with the effects the same had on the activity of PKC epsilon. ET-18-OCH3 progressively inhibited the activity of PKC alpha as the concentration was increased up to 30 mol% of the total lipid, above which the effect was one of activation. The experiments carried out with the homologues showed that the methoxy group bound at the sn-2 position of the glycerol of ET-18-OCH3 is essential for both the initial inhibitory effect and the subsequent activation effect. On the other hand, variations in the type of bond linking substitutions in the sn-1 position, ether or ester, do not seem to play an important role in determining the activity of the enzyme. The effects were different on PKC epsilon since ET-18-OCH3 had a triphasic effect, activating the enzyme at low concentrations, inhibiting it at slightly higher concentrations and then activating it again at higher concentrations. In this case, when the homologues were used, it was observed that the presence of the methoxy group linked to the sn-2 position of glycerol and the type of bond linking substitutions to the sn-1 position were important for activating the enzyme, so that only homologues with ester bonds as LPC and PAPC were able to induce the initial activation step in a way similar to ET-18-OCH3. Substitution of the phosphocholine group of ET-18-OCH3 by phosphoserine led to a greater activation of PKC alpha, an effect that comes from the Ca(2+)-phospholipid binding site probably because of the specific interaction of this site with the phosphoserine group. The action of ET-18-OCH3 and its homologues, as demonstrated in this paper, may permit the selective inhibition or activation of PKC alpha and PKC epsilon by using the most suitable range of concentrations.

Hydrodynamic-based in vivo transfection of retinoic X receptor-alpha gene can enhance vitamin A-induced attenuation of liver fibrosis in mice

BACKGROUND/AIM

In hepatic stellate cells isolated from rat fibrotic livers, the amount of retinoid X receptor-alpha (RXR-alpha) mRNA is greatly reduced. However, the effectiveness of retinoids in the treatment of liver fibrosis is controversial. We hypothesized that increasing the expression levels of RXR-alpha in livers will improve the response of liver fibrosis to retinoids treatment.

METHODS

pTracer-CMV2 vector harboring both green fluorescent protein and RXR-alpha genes was given to mice with carbon tetrachloride (CCl(4))-induced liver fibrosis, by hydrodynamic-based in vivo transfection. Vitamin A was simultaneously administered to the mice. Sirius red staining and measurement of hydroxyproline content were performed to evaluate liver fibrosis. The incorporation of 5-bromo-2-deoxyribouridine (BrdU) was carried out to determine liver cell proliferation.

RESULTS

Successful transfection and expression of exogenous RXR-alpha gene in the liver was determined by observance of green fluorescence under a confocal microscope, and detection of RXR-alpha protein by immunohistochemistry. Hepatic fibrosis, evaluated by both Sirius red staining with image analysis and quantity of hydroxyproline in livers of RXR-alpha-transfected group, tapered off remarkably. The hydroxyproline content and Sirius red-positive staining area on liver sections from RXR-alpha-transfected mice decreased by 34.3% and 54.63%, respectively, compared with the control group receiving empty vector. The labeling index of BrdU in non-parenchymal cells was much lower in livers from the RXR-alpha-transfected group than that of empty vector-transfected group.

CONCLUSIONS

Hydrodynamic-based in vivo transfection of the RXR-alpha gene can enhance the vitamin A-induced attenuation of liver fibrosis in mice. One of the possible mechanisms of action for this gene treatment is inhibition of non-parenchymal cell proliferation mainly composed of hepatic stellate cells in fibrotic livers.